Communication apparatus, control method thereof, and storage medium

ABSTRACT

A communication apparatus includes a transmitting function and a receiving function for a radio signal, and, while belonging to a first group of devices, activates the transmitting and receiving functions to perform communication during a first period, and deactivates the transmitting and receiving functions outside the first period. The communication apparatus determines whether or not it performs monitoring for a presence of a second group of devices during a second period, controls performing of the monitoring by activating the receiving function during the second period when it is determined that the communication apparatus performs such monitoring, and keeping the transmission and receiving functions inactive outside the first period when it is determined that the communication apparatus does not perform such monitoring, and notifies another device in the first group of information related to the second group during the first period when a presence of the second group is detected.

BACKGROUND Field

The present disclosure relates to a communication apparatus, a controlmethod of the communication apparatus, and a storage medium.

Description of the Related Art

Recently, wireless local area networks (LANs) implemented by using theIEEE 802.11 set of standards have been widely used and, accordingly,various network form products and specification standards for wirelessLAN have been developed. US Patent Application Publication No.2014/0302787 describes a neighbor awareness network (NAN) standarddefined by Wi-Fi® Alliance as a standard for a communication apparatusto detect, with a low power consumption, another communication apparatusor a service provided by the other communication apparatus. Using thistechnique, a communication apparatus can synchronize with anothercommunication apparatus the periods of time when it will transmit andreceive information to and from the other communication apparatus. Suchsynchronization allows the communication apparatus to shorten theperiods of time that a radio frequency unit needs to be kept active, andthus can improve the power saving performance of the communicationapparatus. In the below discussion, a communication apparatus thatoperates according to the NAN standard is referred to as a NAN device.Further, the synchronized periods of time when a communication apparatusin a NAN will transmit and receive information from anothercommunication apparatus, is referred to as a discovery window (DW). TheDW period is repeated periodically at regularly occurring intervals, forexample. Further, a group of NAN devices which share a same DW period isreferred to as a NAN cluster.

A NAN device belonging to a NAN cluster operates one of the followingroles: a master, a non-master sync, and a non-master non-sync. A NANdevice that operates as a master periodically transmits asynchronization beacon (hereinafter, referred to as a sync beacon) whichis a beacon used by other terminals to recognize the master NAN device'sDW and synchronize with the master's DW time period. Further, a NANdevice that operates as a master transmits, to a terminal that does notbelong to the NAN cluster, a discovery beacon. A discovery beacon is asignal to assist devices which are not part of a NAN cluster torecognize or detect the NAN cluster. As one example, the discoverybeacon might be transmitted every 100 ms for example during time periodsthat are not a DW period. In each NAN cluster, at least one of the NANdevices operates as a master. A NAN device that operates as a non-mastersync transmits a sync beacon but does not transmit a discovery beacon. ANAN device that operates as a non-master non-sync does not transmit async beacon nor a discovery beacon.

A NAN device that joins a NAN cluster can share information at leastduring any one of the DW periods, regarding the presence of another NANdevice and/or a service or application provided to or from the other NANdevice. For example, NAN devices transmit and receive a subscribemessage, which is a signal searching for a service, and a publishmessage, which is a signal notifying that a certain service is beingprovided, to and from each other. Further, during a DW period, the NANdevice can transmit and receive a follow-up message to exchangeadditional information related to a service. Frame configurations ofmessages such as a publish message, a subscribe message, and a follow-upmessage, are defined in the NAN standard and are referred to as servicediscovery frames (SDFs). A SDF includes a service ID, which is anidentifier for identifying a target service. NAN devices transmit andreceive SDFs to and from each other to find or detect services.

When a NAN device detects a presence of a NAN cluster different from theNAN cluster to which the NAN device belongs, the two different NANclusters can be integrated by merging them. For example, when a NANdevice receives a discovery beacon transmitted from another NAN cluster,the NAN device can compare cluster grades between the first NAN clusterto which the NAN device currently belongs and the newly found second NANcluster. A cluster grade is a property value set for each cluster. Whenthe cluster grade of the second NAN cluster is higher than the clustergrade of the first NAN cluster, the NAN device may join the second NANcluster. When the NAN device's role is that of a master or a non-mastersync, the NAN device that has joined the second NAN cluster transmits,to the first NAN cluster, a sync beacon including information about thesecond NAN cluster which the NAN device has newly joined. Then, the NANdevices in the first NAN cluster receive the sync beacon and join thesecond NAN cluster, and in this way the first NAN cluster is merged withthe second NAN cluster. By integrating the NAN clusters in this manner,a NAN device can search for services from a larger number of NANdevices.

It is assumed that a NAN device is not required to receive datatransmitted from another device outside of the DW periods. However, adiscovery beacon from another NAN cluster may not always be transmittedduring the DW periods of the NAN cluster to which a NAN device belongs.Thus, in order to detect the presence of another NAN cluster and mergetwo NAN clusters, it may be necessary for each NAN device to keep aradio frequency unit active outside of its DW periods, in order to beable to receive a discovery beacon outside of its DW periods. However,when a NAN device always keeps its radio frequency unit active evenoutside of its DW periods, the reduction in consumed power achieved byimplementing a NAN may be canceled or significantly reduced.

SUMMARY

Various embodiments of the present disclosure perform communication suchthat a communication apparatus in one group of communication apparatusescan detect, with a lower power consumption, another group ofcommunication apparatuses.

In some embodiments, a communication apparatus includes a communicationunit having a transmitting function and a receiving function for a radiosignal. While belonging to a first group of devices, the communicationapparatus activates the transmitting function and the receiving functionduring a first period to perform communication, and deactivates thetransmitting function and the receiving function outside the firstperiod. The communication apparatus also includes a determination unitconfigured to determine whether or not the communication apparatus,among devices in the first group, performs monitoring for a presence ofa second group of devices which is different from the first group duringa second period which is different from the first period, a control unitconfigured to control the communication unit by activating the receivingfunction and performing the monitoring during the second period when itis determined that the communication apparatus performs such monitoring,and by keeping the transmitting function and the receiving functioninactive outside the first period when it is determined that thecommunication apparatus does not perform such monitoring, and anotification unit configured to notify another device in the first groupof information related to the second group during the first period whena presence of the second group is detected during the second period.

Further features will become apparent from the following description ofexemplary embodiments (with reference to the attached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration example of a wirelesscommunication system according to one embodiment.

FIG. 2 is a block diagram illustrating a hardware configuration exampleof a NAN device according to one embodiment.

FIG. 3 is a block diagram illustrating a functional configurationexample of the NAN device according to one embodiment.

FIG. 4 is a flowchart illustrating an example of a NAN function startprocess flow according to one embodiment.

FIG. 5 is a flowchart illustrating a first example of an operation modedetermination process flow according to one embodiment.

FIG. 6 is a sequence diagram illustrating an example of a process flowin a wireless communication system according to one embodiment.

FIG. 7 is a diagram illustrating a configuration example of a NAN IEaccording to one embodiment.

FIG. 8 is a flowchart illustrating a second example of a flow of theoperation mode determination process according to one embodiment.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure will be described in detail belowwith reference to the drawings. It is noted that the followingembodiments are simply given as exemplary embodiments and are not to beinterpreted as limiting the content of the present disclosure. Forexample, an example embodiment is described below in which a wirelessLAN system compatible with the neighbor awareness network (NAN) standardis described but the present disclosure is not limited to thisconfiguration. In other words, for example, the following discussion canbe applied to any system in which there are a plurality of communicationgroups that become communicable at predetermined time periods, whichoccur at regular time intervals, where two communication groups can beintegrated to become one communication group based on a signaltransmitted from a communication apparatus in one of the groups to theother group.

In the below description, the standard that the communication apparatusfollows is referred to as the NAN standard, and a network, which isformed according to the NAN standard and used to search and findservices, is referred to as a NAN. Further, as described above, acommunication apparatus, which operates according to the NAN standard,is referred to as a NAN device, and a group of NAN devices which operatein a same discovery window (DW) period is referred to as a NAN cluster.

(Configuration of Wireless Communication System)

FIG. 1 illustrates an example of a configuration of a wirelesscommunication system according to one embodiment. The wirelesscommunication system includes wireless communication apparatuses (NANdevices 101 to 105) that can operate according to the NAN standard. Thewireless communication system may include other communicationapparatuses, for example, such as an access point and a terminal (whichare not illustrated). Further, the NAN devices 101 to 105 may be anydevices as long as the devices are communication apparatuses that canjoin the NAN and perform communications related to an application.

The NAN devices 101 to 105 find a communication apparatus in asurrounding area and a service provided by the communication apparatusaccording to the NAN standard, or allow a NAN device in the surroundingarea to find a service provided by the NAN devices 101 to 105. In theNAN, a group of NAN devices that share a same cycle of turning on an RFfunction is defined as a NAN cluster and the NAN devices are referringto as belonging to the NAN cluster. FIG. 1 illustrates that the NANdevices 101 and 102 belong to a NAN cluster 106 and the NAN devices 103to 105 belong to a NAN cluster 107.

According to the present embodiment, the NAN devices 101 to 105 of theNAN clusters 106 and 107 establish a network with a network of 6 ch(2.437 GHz) with a frequency band of 2.4 GHz. The NAN clusters 106 and107 are NAN clusters in which a length of a DW period is 16 TUs (TimeUnit, 1 TU is 1024 microseconds) and a time interval from a start timingof a DW period to a start timing of a following DW period is 512 TUs.Note that the frequency channel and the DW period used in the NANcluster are not limited to the above example, and any one of a differentfrequency channel and a DW period having a different period length ordifferent intervals may be used.

To each of the NAN devices, a master rank, which is defined in the NANstandard, is set as a factor to decide a role in the NAN cluster. Themaster rank is determined based on a master preference, a random value,and an interface address, which are set for each NAN device. A NANdevice is likely to be allocated with a role as a master when the NANdevice has a higher master rank while a NAN device is likely to beallocated with a role as a non-master non-sync when the NAN device has alower master rank. The NAN device that has a highest master rank in theNAN cluster is referred to as an anchor master and is allocated with arole to be a time reference in the NAN cluster. The NAN standardsuggests that a higher master rank is applied to a NAN device thatconsistently stays in a NAN cluster, such as a NAN device driven by apower source and does not change its location for example. Further, itis suggested that a lower master rank is allocated to a NAN device thatmay not consistently stay in a NAN cluster, such as a device driven by abattery and a mobile terminal. When a NAN device that consistently staysin a NAN cluster serves as a master and transmits synchronizationsignals, the NAN cluster is kept stable.

Further, each NAN cluster is set with a cluster grade, which is definedin the NAN standard. A value of the cluster grade can be calculated asCG=A1×2⁶⁴+A2, where A1 is a master preference of an anchor master and A2is a time synchronization function (TSF) value. The NAN standard definesthat, when a NAN device finds a NAN cluster which is different from theNAN cluster to which the NAN device belongs, these NAN clusters aremerged, to the NAN cluster with a higher cluster grade.

(Configuration of NAN Device)

FIG. 2 illustrates a hardware configuration example of the NAN device101. Here, only the NAN device 101 will be described in this example;however, the NAN devices 102 to 105 also have the same configuration.The NAN device 101 includes a storage unit 201, a control unit 202, afunctional unit 203, an input unit 204, an output unit 205, acommunication unit 206, and an antenna 207, for example, as its hardwareconfiguration.

The storage unit 201 is configured with both of a ROM and a RAM or oneof the ROM and RAM, and stores a later described program for performingvarious operations or various information such as a communicationparameter used in wireless communication. Here, the ROM is an acronymstanding for a read only memory and the RAM is an acronym standing for arandom access memory. Here, as the storage unit 201, a storage mediumsuch as a flexible disk, a hard disk, an optical disk, a magneticoptical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memorycard, and a DVD may be used in addition to the memory including the ROMand RAM.

The control unit 202 is composed of a CPU or an MPU, and controls theNAN device 101 overall by executing a program stored in the storage unit201. Here, the CPU is an acronym standing for a central processing unit,and the MPU is an acronym standing for a micro processing unit. Here,the control unit 202 may control the NAN device 101 overall incooperation with the program stored in the storage unit 201 and an OS.Here, the OS is an acronym standing for an operating system. Further,the control unit 202 controls the functional unit 203 and executes apredetermined process such as imaging, printing, projecting, and thelike.

The functional unit 203 is a hardware used by the NAN device 101 toexecute a predetermined process. For example, in a case that the NANdevice 101 is a camera, the functional unit 203 serves as an imagepickup unit and performs an image pickup process. Further, for example,in a case that the NAN device 101 is a printer, the functional unit 203serves as a printing unit and performs a printing process. Further, forexample, in a case that the NAN device 101 is a projector, thefunctional unit 203 serves as a projecting unit and performs aprojecting process. The data processed in the functional unit 203 may bethe data stored in the storage unit 201 or the data acquired fromanother NAN device via later described communication unit 206.

The input unit 204 accepts various operations by a user. The output unit205 performs various outputs to the user. Here, the outputs from theoutput unit 205 include at least one of a display on a screen, a soundoutput from a speaker, a vibration output, and the like. Here, both ofthe input unit 204 and output unit 205 may be realized in a singlemodule such as a touch panel.

The communication unit 206 controls wireless communication compatiblewith IEEE 802.11 series and controls IP communication. IP is an acronymstanding for Internet Protocol. Further, the communication unit 206controls the antenna 207 and transmits and receives radio signals forwireless communication. The NAN device 101 transmits and receivescontents such as image data, text data, video data, and the like to andfrom another NAN device via the communication unit 206.

In one embodiment, the communication unit 206 has a signal transmittingfunction and a signal receiving function and can activate or deactivatethose functions separately and independently according to an instructionfrom the control unit 202. It is assumed that the transmitting functionand receiving function consume power while being active and do notconsume power or consume less power when in the inactive state, ascompared to the activate state.

FIG. 3 illustrates a functional configuration example of the NAN device101. In this example, only the NAN device 101 will be described;however, the NAN devices 102 to 105 have the same configuration. The NANdevice 101 includes a wireless LAN control unit 301, a NAN control unit302, an application control unit 303, and an operation control unit 304for example, as a functional configuration.

The wireless LAN control unit 301 performs control for transmitting andreceiving a radio signal according to a signal format of a correspondingwireless LAN to and from another communication apparatus that cancommunicate via the wireless LAN. Further, to wireless LAN control unit301 executes various controls related to the wireless LAN according toseries of IEEE 802.11 standards. The NAN control unit 302 executesvarious controls of service searching and fining, and the like accordingto the NAN standard. Further, the NAN control unit 302 executes a NANfunction start process and an operation mode determination process,which will be described in the following. The NAN control unit 302controls the wireless LAN control unit 301 according to an operationmode determined in the operation mode determination process. The NANcontrol unit 302 has a function for reducing power consumption by thecommunication unit 206 of FIG. 2 and improving its power savingperformance by controlling the wireless LAN control unit 301 todeactivate at least one of the transmitting function and receivingfunction for a preferable period of time.

The application control unit 303 causes the NAN control unit 302 tostart or end the NAN function in response to the application process.Then, the NAN control unit 302 establishes a network with a device foundby the NAN function and the wireless LAN control unit 301 transmits andreceives application data under the control by the application controlunit 303. For example, when a user (not illustrated) of the NAN device101 starts an image sharing service application that uses NAN, theapplication control unit 303 instructs the NAN control unit 302 toperform a NAN function start process. After that, the NAN control unit302 establishes a network with the found device according to the seriesof IEEE 802.11 standards by controlling the wireless LAN control unit301 and, transmits and receives image data via the established network.On the other hand, when the user of the NAN device 101 ends theapplication, the application control unit 303 instructs the NAN controlunit 302 to perform a NAN function end process. Note that thetransmission of the application data may be performed according toanother communication standard other than the NAN standard.

The operation control unit 304 accepts and manages an operation by theuser of the NAN device 101 and, in response to the operation, transfersa proper signal at a proper timing to the wireless LAN control unit 301,NAN control unit 302, and application control unit 303 respectively.

(Process Flow)

Next, an example of a process flow executed by the above described NANdevice 101 will be described. In the following discussion, a processexecuted by the NAN device 101 will be described; however, the NANdevices 102 to 105 can also execute the same process.

In the following embodiment, the NAN device 101 generates a NAN clusteror joins an existing NAN cluster, and activates its transmittingfunction and receiving function in a DW period which comes in a firstcycle related to the NAN cluster 106 to which the NAN device 101belongs. Then, the NAN device 101 determines whether or not the NANdevice 101 among the devices in the NAN cluster 106 monitors a presenceof another NAN cluster outside the DW period and, according to thedetermination, determines whether or not to activate its receivingfunction during a predetermined period of time outside the DW period.Here, the predetermined period of time is set to be a period longer thana maximum transmission period a discovery beacon. When the NAN device101 determines that the NAN device 101 monitors a presence of anotherNAN cluster outside the DW period, the NAN device 101 deactivates itstransmitting function and receiving function except for the DW periodfor the NAN cluster to which the NAN device 101 belongs and thepredetermined period of time. With this action, the NAN device 101 cansuppress its power consumption since the transmitting function andreceiving function are not kept active all the time. Then, when the NANdevice 101 detects a presence of another NAN cluster outside the DWperiod, the NAN device 101 notifies another device, which belongs to theNAN cluster 106, that another NAN cluster has been found during the DWperiod of the NAN cluster 106. Further, when it is determined thatanother device in the NAN cluster 106 monitors a presence of another NANcluster during the above predetermined period and the NAN device 101does not perform the monitoring, the NAN device 101 deactivates thetransmitting function and receiving function outside DW period. In thiscase, the NAN device 101 can receive a notification of a result of themonitoring from the another device in the NAN cluster 106 during the DWperiod of the NAN cluster 106. In this manner, since the NAN device 101deactivates its communication function outside the DW period when theNAN device 101 dose not monitor a presence of another NAN cluster, andlimits the period to execute the monitoring when the NAN device 101executes the monitoring, the power consumption can be reduced. The powerconsumption of the entire system can be significantly reduced when alarger number of NAN devices in the wireless communication systemperform this process.

In the following, the above process will be described in detail.

First Embodiment

FIG. 4 illustrates an example of the NAN function start process flow,which is executed by the NAN control unit 302. The NAN function startprocess is a process executed when the NAN device 101 starts the NANfunction. The NAN device 101 may start the NAN function when an imagesharing service application using NAN is activated or when the power ofthe NAN device 101 is turned on, for example. Here, the flowchartillustrated in FIG. 4 can be realized when the control unit 202 of theNAN device 101 executes a control program stored in the storage unit 201and controls calculating and processing of information and eachhardware.

In this process, the NAN device 101 firstly executes passive scanning ofa NAN cluster being in a surrounding area (S401). The NAN device 101according to the present embodiment scans 6 ch in the passive scanning.When a discovery beacon or a synchronization beacon (hereinafter,referred to as a sync beacon) is received, the NAN device 101 determinesthat a NAN cluster is found (YES in S402). On the other hand, when sucha beacon is not received, the NAN device 101 determines that a NANcluster has not found (NO in S402).

When a NAN cluster is not found (NO in S402), the NAN device 101 judgeswhether or not a certain period of time has passed since the passivescanning starts (S403), the process returns to S401 in a case that thecertain period of time has not passed (NO in S403). On the other hand,when it is judged that the certain period of time has passed withoutfinding a NAN cluster (YES in S403), the NAN device 101 ends the passivescanning and generates a NAN cluster (S404). When generating a NANcluster, the NAN device 101 generates a new NAN cluster including theNAN device 101 itself and serves as an anchor master to execute aprocess specified in the NAN standard, such as transmission of adiscovery beacon or a sync beacon and the like.

In this case, the above certain period of time is two minutes as anexample; however, this example does not set any limitation and anylength of time may be set as the certain period of time here. Also, inpassive scanning, the receiving function of the communication unit 206needs to be activated at least in a certain period of time and, when theperiod of activating the function becomes longer, the consumed powerbecomes greater. Therefore, also in the passive scanning, a period thatthe receiving function of the communication unit 206 is made active maybe set as a certain period of time which is equal to or longer than 200TUs, the maximum cycle of a discovery beacon, as executed in a laterdescribed merge management operation mode. With this configuration,since the NAN device 101 can find a NAN cluster in a short time when adiscovery beacon is transmitted in a surrounding area, the receivingfunction does not have to be kept active unnecessarily for a long periodof time.

When a NAN cluster is found in S402 (YES in S402), the NAN device 101joins the found NAN cluster (S405). When joining the NAN cluster, theNAN device 101 synchronizes with the DW of the NAN cluster and executesa process defined in the NAN standard according to the information ofthe NAN cluster received during the passive scanning.

After the process in S404 or S405, the NAN device 101 executes theoperation mode determination process (S406). The operation modedetermination process will be described later.

As the operation mode, there are a merge management mode and a powersaving mode. In the merge management mode, the receiving function of thecommunication unit 206 is activated for a certain period of time outsidethe DW period to monitor a presence of another NAN cluster. Since thereceiving function of the communication unit 206 is activated outsidethe DW period, a possibility of receiving a discovery beacon or a syncbeacon transmitted from another NAN cluster can be made higher. In oneembodiment, the certain period of time in this example can be set equalto or loner than 200 TUs, for example. This is because, in the NANstandard, a discovery beacon is supposed to be transmitted every 200 TUsas long as the timing does not occur during the DW period. In thisembodiment, when the timing of transmitting a discovery beacon occursduring the DW period, the transmission of a discovery beacon can beskipped and a sync beacon is required to be transmitted in the DWperiod. Thus, by setting the above certain period of time to be equal toor longer than 200 TUs, the NAN device 101 can receive a discoverybeacon or a sync beacon and find another NAN cluster within the period.According to the present embodiment, the receiving function is activatedonce between the DW periods; however, the receiving function may beactivated twice between two DW periods for example; these examples donot set any limitation.

In the merge management mode, as described above, when a NAN cluster,which is different from the NAN cluster to which the NAN device 101currently belongs, is found, the NAN device 101 performs a merge processof the NAN cluster according to the NAN standard. In other words, theNAN device 101 compares cluster grade of the first NAN cluster to whichit currently belongs and the cluster grade of the found second NANcluster and, when the cluster grade of the second NAN cluster is higher,the NAN device 101 joins the second NAN cluster. After that, the NANdevice 101 transmits a sync beacon during the DW period of the first NANcluster to which the NAN device 101 has been belonged. To the syncbeacon, a NAN IE (information element) is applied and a cluster. ID ofthe second NAN cluster is stored in A3 address field in NAN IE. Withthis configuration, the NAN device 101 can notify another NAN device inthe first NAN cluster of a presence of a second NAN cluster.

On the other hand, the NAN device 101 operates to suppress its powerconsumption by not activating (deactivating) the receiving function ofthe communication unit 206 outside the DW period, in the power savingmode. In the power saving mode, finding and merging of another NANcluster is performed by receiving the sync beacon transmitted fromanother NAN device which operates in the merge management mode. Thedetails of this process will be described later. Here, the operationduring the DW period and a discovery beacon transmission process outsidethe DW period are performed according to the NAN standard in bothoperation modes.

At this point, according to the present embodiment, the NAN device 101performs the NAN function start process in order of the processes in theflowchart illustrated in FIG. 4; however, the NAN cluster generation inS404 or the operation mode determination process in S406 may be executedbefore the passive scanning in S401. In this case, the NAN device 101may execute the passive scanning in S401 for a certain period of timeafter the operation mode determination process.

Next, with reference to FIG. 5, a first example of the operation modedetermination process flow that the NAN device 101 executes in S406 willbe described. Here, the flowchart illustrated in FIG. 5 may be realizedby the control unit 202 of the NAN device 101 executing a controlprogram stored in the storage unit 201 and controlling calculating andprocessing of information and each hardware.

The NAN device 101 firstly determines which of the three roles—a master,a non-master sync, and a non-master non-sync—it is performing in the NANcluster according to the NAN standard (S501). In the NAN standard, allthe NAN devices at the timing of generating a NAN cluster and at thetiming of joining a NAN cluster operate as a master. After that, the NANdevice changes its role to a non-master sync or a non-master non-syncaccording to need, based on the sync beacon received during the DWperiod. The NAN device changes its role according to a received signalstrength indicator (RSSI) value of the sync beacon, a master rank of thesync beacon, an AMR value, and a hop count field value, for example.Here, the AMR is an abbreviation of an anchor master rank. When the roleof the NAN device does not change for equal to or more than two DWperiods, the NAN device judges that its role has settled and the roledetermination process can be ended; however, this example does not setany limitation and this process may be continued for a predeterminedperiod of time, for example. Here, the role may be changed when the syncbeacon is received during the DW period, or at the timing when the DWperiod ends. Thus, every time when the role is changed, a process fromS501 of FIG. 5 may be executed. With this configuration, the operationmode can be properly switched every time when the role is changed.

After that, the NAN device 101 determines whether or not the role is anon-master non-sync (S502). Then, when its role is not a non-masternon-sync (NO in S502), the NAN device 101 determines to operate in amerge management mode (S503). Further, when its role is a non-masternon-sync, the NAN device 101 determines to operate in a power savingmode (S504). In other words, when its role is to transmit a sync beacon,the NAN device 101 operates in the merge management mode and, in othercases, the NAN device 101 operates in the power saving mode.

As described above, since an RSSI value of the sync beacon is used as afactor in the role determination according to the NAN standard, the NANdevice determines whether or not to change its role based on whether ornot the RSSI value is equal to or greater than a predetermined thresholdvalue. In other words, when the RSSI value is equal to or greater thanthe threshold value, the NAN device shifts from a master to a non-mastersync, and further, shifts its role from a non-master sync to anon-master non-sync. Since the RSSI value is basically proportional to adistance between the transmitting and receiving devices, there is likelyto be a NAN device of a master or a non-master sync near the NAN deviceof a non-master non-sync. Thus, even when operating in the power savingmode, the NAN device of a non-master non-sync can acquire information ofanother NAN cluster from a NAN device which operates as a master or anon-master sync.

In FIG. 5, an example that the operation mode is switched according towhether or not the NAN device is a non-master non-sync has beenexplained; however, the operation mode may be switched based on whetheror not the NAN device is a master. In other words, in a case of amaster, the NAN device operates in the merge management mode and, in acase of a non-master sync or a non-master non-sync, the NAN deviceoperates in the power saving mode. In this case, since the NAN deviceoperates in the merge management mode only in a case of a master, thepossibility of operating in the power saving mode becomes higher and thepower saving performance can be further improved.

Next, with reference to FIG. 6, an example of a process flow executed inthe wireless communication system will be described. In the followingexplanation, it is assumed that the master rank of the NAN device 101 ishigher than the master rank of the NAN device 102 and the NAN device 103continues to operate as a master of the NAN cluster 107. Here, in FIG.6, the NAN devices 104 and 105 are omitted in purpose of simplificationof the explanation. Further, it is assumed that the cluster grade of theNAN cluster 107 is higher than that f the NAN cluster 106. Further, inthis process example, it is assumed that the NAN device 102 searches animage sharing service and the device that can provide the image sharingservice is only the NAN device 103.

In FIG. 6, firstly, the NAN functions of the NAN devices 101 and 103 arestarted by the users of the respective devices and it is assumed thatthe NAN devices 101 and 103 start the NAN functions (S601 and S603).Here, it is assumed that there is not another NAN device in searchingareas of the NAN devices 101 and 103 respectively and, further, the NANdevices 101 and 103 are located in areas where radio waves do not reacheach other. Then, the NAN devices 101 and 103 perform passive scanningas described with reference to FIG. 4; however, another NAN devicecannot be found for a certain period of time. Thus, the NAN devices 101and 103 generate the NAN clusters 106 and 107 respectively (S602 andS604).

Here, since there is not any NAN device in respective vicinity areas,the NAN devices 101 and 103 determine the roles of the NAN devices 101and 103 as a master as described related to S501 of FIG. 5. Then, asdescribed related to S503 of FIG. 5, the NAN devices 101 and 103 bothoperate in the merge management mode. In this case, since the NANdevices 101 and 103 are only the NAN device in the respective NANclusters, the NAN devices 101 and 103 operate as an anchor master.

Then, after the NAN device 101 generates the NAN cluster 106, the NANfunction of the NAN device 102 is activated by user's operation and itis assumed that the NAN function of the NAN device 102 is started(S605). Then, the NAN device 102 starts passive scanning. During thisperiod, since the NAN device 101 periodically transmits a discoverybeacon (S606), the NAN device 102 can find the NAN cluster 106 generatedby the NAN device 101 during the passive scanning. Then, the NAN device102 can join the NAN cluster 106 to which the NAN device 101 belong(S607). Here, at this timing, the NAN device 102 initially determinesits role as a master, according to the NAN standard.

When the NAN device 102 joins the NAN cluster 106, the NAN device 102performs a role determination as described in S501 to fix its role. Inthis example, as described above, the master rank of the NAN device 101is higher than that of the NAN device 102. Further, the NAN device 102is assumed to receive a radio wave from the NAN device 101 with a RSSIvalue larger than the threshold value, which is RSSI_close, defined inthe NAN standard. In this case, when a sync beacon transmitted from theNAN device 101 during the DW period of the NAN cluster 106 is received,the NAN device 102 shifts its role from a master to a non-master sync.Here, an AMR value of the NAN device 102 is rewritten with an AMR valueincluded in the received sync beacon, and a hop count value is set to avalue in which one is added to a hop count value included in the syncbeacon (which is “1”). Since the NAN device 101 is an anchor master, theAMR value included in the sync beacon transmitted from the NAN device101 becomes a value of the master rank of the NAN device 101 and the hopcount value becomes zero.

The NAN device 102 receives the sync beacon retransmitted from the NANdevice 101 during a following DW period. In this case, the AMR value ofthe NAN device 102 and the AMR value of the received sync beaconcorrespond to each other, and the hop count value of the sync beacon issmaller than the hop count value of the NAN device 102. Thus, the NANdevice 102 shifts its role from a non-master sync to a non-masternon-sync according to the NAN standard. When the configuration of theNAN cluster 106 is not changed during and after a following DW period,the NAN device 102 receives the same sync beacon. Thus, the NAN device102 keeps operating as a non-master non-sync without changing its role.As a result, the NAN device 102 determines to operate in the powersaving mode.

Here, the NAN device 102 broadcasts a subscribe message in the DW periodof the NAN cluster 106 to search an image sharing service (S608). TheNAN device 101 can receive the subscribe message but does not transmit apublish message since the NAN device 101 cannot provide the imagesharing service. On the other hand, the radio wave from the NAN device102 does not reach the NAN device 103. Or the NAN device 103 cannotreceive the subscribe message from the NAN device 102 since the NANdevice 103 belongs to the NAN cluster 107, which is different from theNAN cluster 106 that the NAN device 102 belongs to, has a different DWperiod.

After that, it is assumed that the NAN device 103 moves (S609) and theNAN device 101 becomes able to receive a discovery beacon from the NANdevice 103.

In this case, since the NAN device 101 is operating in a mergemanagement mode, the NAN device 101 also keeps the receiving function ofthe communication unit 206 active outside the DW period to find anothercluster. Here, the NAN device 101 may keep the transmitting function ofthe communication unit 206 inactive. In other words, the NAN device 101activates both of the transmitting function and receiving functionduring the DW period of the NAN cluster to which the NAN device 101belongs and, in the merge management mode, the transmitting function canbe deactivated while the receiving function is activated during apredetermined period of time outside the DW period. Further, the NANdevice 101 may deactivate both of the transmitting function andreceiving function during a period which is not either of the DW periodnor the above predetermined period. Further, the NAN device 101 sets thepredetermined period to be equal to or longer than 200 TUs, which is amaximum transmission cycle of a discovery beacon defined in the NANstandard. With this configuration, the possibility that the NAN device101 can receive a discovery beacon transmitted from a NAN cluster whichis different from the NAN cluster 106 to which the NAN device 101belongs can be increased. With this, the NAN device 101 receives thediscovery beacon of the NAN device 103 (S610).

Here, as described above, since the NAN cluster 107 has a higher clustergrade than that of the NAN cluster 106, the NAN device 101 joins the NANcluster 107 by a NAN cluster merge process defined in the NAN standard(S611). Then, the NAN device 101 transmits a sync beacon during the DWperiod of the NAN cluster 106 (S612). The sync beacon is applied with aNAN IE including a cluster ID of the NAN cluster 107 in an A3 addressfield. Here, according to the present embodiment, a sync beacon is usedto give notice of information of the NAN cluster 107; however, othersignals such as a probe response may be used. Further, the NAN device101 notifies the NAN device 102 of information of the NAN cluster 107after joining the NAN cluster 107; however, the NAN device 101 maynotify the NAN device 102 of information of the NAN cluster 107 beforejoining the NAN cluster 107.

The NAN device 102 is operating in a power saving mode, and thereceiving function of the communication unit 206 is deactivated outsidethe DW period. Thus, there may be a case that the NAN device 102 cannotreceive a discovery beacon in S610. However, the NAN device 102 canreceive the sync beacon of S612 since the sync beacon is transmittedduring a period when the receiving function of the communication unit206 is active. Therefore, the NAN device 102 can receive information ofthe NAN cluster 107 from the sync beacon and join the NAN cluster 107(S613).

When the NAN device 102 joins the NAN cluster 107, the NAN device 102broadcasts a subscribe message again during the DW period of the NANcluster 107 to search an image sharing service (S614 and S615). In thiscase, the NAN device 103 is able to provide an image sharing service.Thus, the NAN device 103 transmits a publish message in response to thesubscribe message (S616) and notifies the NAN device 102 that the NANdevice 103 can provide the image sharing service.

After that, the NAN devices 102 and 103 transmit and receive image databy data communication (S617). Here, the data communication in S617 maybe performed by a NAN connection or may be performed by establishinganother connection of another communication standard such as Wi-FiDirect®.

In this manner, according to the present embodiment, a NAN deviceoperating in a role other than a non-master non-sync monitors a presenceof another cluster and notifies a NAN device operating in a role of anon-master non-sync of the result. Thus, since the NAN device operatingin a role of a non-master non-sync deactivates the receiving functionand transmitting function of the communication unit 206 outside the DWperiod, the NAN clusters can be merged while saving power consumption ofthe entire system. Particularly, under a condition that a large numberof NAN devices exist in a certain range, since more NAN devices operateas a non-master non-sync, the power saving performance of the entiresystem can be significantly improved.

Second Embodiment

According to the present embodiment, a NAN device operating in a mergemanagement mode explicitly notifies another NAN device belonging to thesame NAN cluster that the NAN device is operating in a merge managementmode. According to the first embodiment, it may be considered that theNAN device operating in a power saving mode operates assuming that anotification of information of another NAN cluster can be received froma NAN device in a surrounding area. On the other hand, according to thepresent embodiment, a NAN device operating in a power saving mode canexplicitly know that information is to be notified when another NANcluster is found, by receiving a notification, from a NAN device in asurrounding area, that the NAN device is operating in a merge managementmode. Further, when there is a NAN device operating in a mergemanagement mode in a surrounding area, the NAN device stops itsoperation in the merge management mode and switches to a power savingmode so that the power saving performance of the entire system can beimproved. In the following discussion, one feature different from thefirst embodiment will be described.

According to the present embodiment, the NAN device operating in themerge management mode notifies another NAN device in the NAN cluster towhich the NAN device belongs that the NAN device operates in the mergemanagement mode by using a sync beacon. In this embodiment, in additionto this, the NAN device operating in the merge management mode mayperform the above notification by publishing a merge management serviceby using SDF of the NAN standard. Further, the NAN device may performthe above notification according to a communication standard other thanNAN. Further, the NAN device may perform the above notification bynegotiation with devices of another method in advance.

The sync beacon includes NAN IE 700 as illustrated in FIG. 7, and, toNAN IE 700, one or more NAN attribute 701 can be applied. The NANattribute 701 includes an attribute ID 702, which is an identifier, anattribute body field 704, which is a property content, and a length 703that indicates its length. As a value to be stored in the attribute ID,there is a value defined in the standard, a vendor specific attributethat is unique in each vendor and extensible, and a reserved, which hasnot been used at this point. According to the present embodiment, anattribute ID “14” as a reserved is used as an attribute to give noticeof an operation in a merge management mode. However, it is not limitedto this example and other values may be used. Further, for example, whenthe attribute ID is “14,” the length is set as “1,” and it is assumedthat “0” of the attribute body field 704 represents an operation in amerge management mode and “1” represents an operation in power savingmode. Each NAN device can recognize operation modes of NAN device in thesurrounding area with reference to the attribute body field 704 of areceived sync beacon. Here, a value of a data field may be set to anyvalue and it is not limited to the above content.

The NAN device in the first embodiment switches the operation modeaccording to its role, and the NAN device in the present embodimentswitches its operation mode according to an operation mode of a NANdevice in a surrounding area. Here, according to the present embodiment,as an example, the NAN device is assumed to operate in a mergemanagement mode at a timing of generating a NAN cluster or a timing ofjoining a NAN cluster. Then, the NAN device receives a sync beaconhaving a NAN IE of the above described attribute ID of “14,” and changesits operation mode to the power saving mode when it is detected thatanother NAN device in the surrounding area is operating in a mergemanagement mode. On the other hand, the NAN device changes its operationmode to the merge management mode when all. NAN devices in a surroundingarea operate in a power saving mode and the NAN device itself isoperating in a power saving mode. With this configuration, since the NANdevice operates in a power saving mode when there is another NAN deviceoperating in a merge management mode in a surrounding area, the powerconsumption of the entire system can be reduced.

Next, an operation mode determination process according to the presentembodiment will be described with reference to FIG. 8. Here, a processexecuted by the NAN device 101 will be explained; however, the NANdevices 102 to 105 can execute the similar process. Further, theflowchart illustrated in FIG. 8 can be realized by the control unit 202of the NAN device 101 executing a control program stored in the storageunit 201 and executing a control calculating and processing ofinformation and each hardware.

In this process, the NAN device 101 firstly performs mode monitoring ofanother NAN device (S801). The mode monitoring of another NAN device isperformed by receiving a sync beacon transmitted from another NAN deviceand monitoring the attribute body field 704 of NAN IE 700 included inthe sync beacon. When the attribute body field 704 of the received syncbeacon is “0,” the NAN device 101 can recognize that there is a NANdevice which is operating in a merge management mode.

When it is not determined that there is a NAN device operating in amerge management mode by the mode monitoring of other NAN devices (No inS802), the NAN device 101 continues the mode monitoring of other NANdevices for a certain period of time (NO in S803). The certain period oftime here is 200 TUs for example; however, this example does not set anylimitation.

When it is determined that there is another NAN device operating in amerge management mode within the certain period of time (YES in S802),the NAN device 101 decides to operate in a power saving mode (S805). Onthe other hand, when it cannot be determined that there is another NANdevice in a merge management mode after the certain period of time (YESin S803), the NAN device 101 decides to operate in a merge managementmode (S804).

The NAN device 101 can execute the process in FIG. 8 every time when async beacon of an attribute ID of “14” is received from another NANdevice, but is not limited to this. For example, after executing theprocess of FIG. 8 once, the NAN device 101 may not execute the processof FIG. 8 for a certain period of time to reduce process load.

Here, when a notification that an operation in a merge management modeis received from another device in a surrounding area, the NAN device101 does not have to switch to the power saving mode immediately. Forexample, the NAN device 101 compares a master rank of the NAN device,which is a sender of the notification with the master rank of the NANdevice 101 and, when the master rank of the NAN device 101 is lower, itis decided to operate in a power saving mode. This configuration canprevent both of the two NAN devices from switching to a power savingmode, in a case that the two NAN devices notify each other that they areoperating in a merge management mode. Further, in a case that the masterranks of the two NAN devices are the same, the operation modes of theseNAN devices may be kept as the merge management mode. Further, in a casethat all NAN devices in a surrounding area are in a power saving mode,the NAN device 101 may compare master ranks of those NAN devices in thesurrounding area with the master rank of the NAN device 101. Then, theNAN device 101 may shift to a merge management mode only when its masterrank is higher than any of the NAN devices in the surrounding area. Thisconfiguration can prevent the power consumption of the entire systemfrom increasing as the plurality of NAN devices switch to a mergemanagement mode when all the NAN devices in the surrounding area are ina power saving mode. Here, in a case that there are a plurality of NANdevices having highest master rank, two or more NAN devices among theplurality of NAN devices may shift to a merge management mode.

According to the present embodiment, by adding a function to setattribute ID of “14” of NAN IE to the NAN standard and give notice of anoperation mode, the NAN devices are allowed to notify each other oftheir operation modes (a merge management mode or a power saving mode).With this configuration, a NAN device operating in a power saving modecan explicitly recognize that there is a NAN device operating in a mergemanagement mode in a surrounding area and, when there is a NAN clusterto merge, can surely join the NAN cluster. Further, when there is noother NAN device operating in a merge management mode in a surroundingarea, the NAN device can promptly recognize a NAN cluster and join theNAN cluster by operating in the merge management mode.

Here, the first and second embodiments may be combined. In other words,the NAN device may decide its operation mode according to both of itsroll and an operation mode of another NAN device.

Other Embodiments

Embodiment(s) of the present disclosure can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Biu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While exemplary embodiments have been described, it is to be understoodthat the present disclosure is not limited to the disclosed exemplaryembodiments. The scope of the following claims is to be accorded thebroadest interpretation so as to encompass all such modifications andequivalent structures and functions.

This application claims the benefit of Japanese Patent Application No.2016-141824, filed Jul. 19, 2016, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A communication apparatus comprising: acommunication unit having a transmitting function and a receivingfunction for a radio signal, wherein, while belonging to a first groupof devices, the communication apparatus activates the transmittingfunction and the receiving function to perform communication during afirst period, and deactivates the transmitting function and thereceiving function outside of the first period; a determination unitconfigured to determine whether or not the communication apparatus,among devices in the first group, performs monitoring for a presence ofa second group of devices which is different from the first group duringa second period which is different from the first period; a control unitconfigured to control the communication unit by activating the receivingfunction and performing such monitoring during the second period when itis determined that the communication apparatus performs such monitoring,and by keeping the transmitting function and the receiving functioninactive outside the first period when it is determined that thecommunication apparatus does not perform the monitoring; and anotification unit configured to notify another device in the first groupof information related to the second group during the first period whena presence of the second group is detected during the second period. 2.The communication apparatus according to claim 1, wherein thedetermination unit determines that the communication apparatus performsthe monitoring when the communication apparatus is operating in a rolethat transmits a beacon, and determines that the communication apparatusdoes not perform the monitoring when the communication apparatus isoperating in a role that does not transmit a beacon.
 3. Thecommunication apparatus according to claim 1, wherein the determinationunit determines that the communication apparatus performs the monitoringwhen the communication apparatus is operating in a role that transmits asignal to be found by another device in the first group, and determinesthat the communication apparatus does not perform the monitoring whenthe communication apparatus is operating in a role that does nottransmit the signal.
 4. The communication apparatus according to claim1, wherein the second period has a length equal to or longer than acycle that a signal for assisting another device to find the secondgroup is transmitted in a case where there is the second group.
 5. Thecommunication apparatus according to claim 1, wherein the monitoring fora presence of a second group is performed by receiving a discoverybeacon, which is transmitted from a device in the second group,according to the neighbor awareness network (NAN) standard.
 6. Thecommunication apparatus according to claim 2, wherein the determinationunit determines whether or not the communication apparatus performs themonitoring every time the role of the communication apparatus changes.7. The communication apparatus according to claim 1, wherein thedetermination unit further determines which of another device or thecommunication apparatus is to perform the monitoring when it isnotified, from the another device the first group, that the anotherdevice is performing the monitoring and the communication apparatus isalso performing the monitoring.
 8. The communication apparatus accordingto claim 1, wherein the determination unit further determines which ofanother device or the communication apparatus is to perform themonitoring when it is not notified, from the another device in the firstgroup, that the another device is performing the monitoring and thecommunication apparatus is not performing the monitoring either.
 9. Thecommunication apparatus according to claim 7, wherein the furtherdetermination is made based on values of master ranks of the anotherdevice and the communication apparatus according to the neighborawareness network (NAN) standard.
 10. The communication apparatusaccording to claim 1, wherein the determination unit determines that thecommunication apparatus is not to perform the monitoring when it isnotified, from another device in the first group, that the anotherdevice is performing the monitoring, and determines that thecommunication apparatus is to perform the monitoring when it is notnotified, from the another device in the first group, that the anotherdevice is performing the monitoring.
 11. The communication apparatusaccording to claim 1, wherein the notification unit does not give noticeof information related to the second group when the second group ismerged with the first group, even in a case where a presence of thesecond group is detected during the second period.
 12. The communicationapparatus according to claim 1, wherein the notification unit notifiesinformation related to the second group, when a presence of the secondgroup is detected during the second period and the first group is mergedwith the second group.
 13. The communication apparatus according toclaim 1, wherein the notification unit notifies information related tothe second group after joining the second group.
 14. The communicationapparatus according to claim 1, wherein the communication unitdetermines that there is a second group when, during the second period,a signal to assist other devices to find the second group or a signaltransmitted during a third period during which a device in the secondgroup can communicate, is received.
 15. The communication apparatusaccording to claim 1, wherein the first group and the second group areNAN clusters according to the neighbor awareness network (NAN) standard.16. A control method a communication apparatus that includes acommunication unit having a transmitting function and receiving functionfor a radio signal, wherein, while belonging to a first group ofdevices, the communication apparatus activates the transmitting functionand the receiving function to perform communication in a first period,and deactivates the transmitting function and the receiving functionoutside the first period, the control method comprising: determiningwhether or not the communication apparatus, among devices in the firstgroup, performs monitoring for a presence of a second group of deviceswhich is different from the first group during a second period which isdifferent from the first period; controlling the communication unit byactivating the receiving function and performing such monitoring duringthe second period when it is determined that the communication apparatusperforms such monitoring, and by keeping the transmitting function andthe receiving function inactive outside the first period when it isdetermined that the communication apparatus does not perform themonitoring; and notifying another device in the first group ofinformation related to the second group during the first period when apresence of the second group is detected during the second period.
 17. Anon-transitory computer readable storage medium storing a program thatcauses a communication apparatus to perform processes, the communicationapparatus including a communication unit having a transmitting functionand a receiving function for a radio signal, wherein, while belonging toa first group of devices, the communication apparatus activates thetransmitting function and the receiving function to performcommunication in a first period, and deactivates the transmittingfunction and the receiving function outside the first period, theprocesses comprising: determining whether or not the communicationapparatus, among devices in the first group, performs monitoring for apresence of a second group of devices which is different from the firstgroup during a second period which is different from the first period;controlling the communication unit by activating the receiving functionand performing the monitoring during the second period when it isdetermined that the communication apparatus performs such monitoring,and by keeping the transmitting function and the receiving functioninactive outside the first period when it is determined that thecommunication apparatus does not perform such monitoring; and notifyinganother device in the first group of information related to the secondgroup during the first period when a presence of the second group isdetected during the second period.